Hamilton–Norwood scale

The Hamilton–Norwood scale is used to classify the stages of male pattern baldness. It is one of the widely accepted and reproducible classification system for the male pattern hair loss (androgenetic alopecia). The stages are described with a number from 1 to 7 with a type A variant for the cases with anterior involvement.

Overview
Androgenetic alopecia follows a defined pattern of hair loss, beginning with bitemporal recession of the frontal hairline. Eventually, diffuse thinning over the vertex (top) of the scalp occurs. With progression, complete hair loss in this region is common. The bald patch progressively enlarges and eventually joins the receding frontal hairline.

This measurement scale was first introduced by James Hamilton in the 1950s and later revised and updated by O'Tar Norwood in the 1970s. It is sometimes referred to as the Norwood–Hamilton scale or simply the Norwood scale.

The scale is regularly used by doctors to assess the severity of baldness, but it is not considered very reliable since examiners' conclusions can vary.

Diagnostic
Dermatologists might use the Norwood Scale on patients to assess male pattern baldness. It is especially used to check if hair loss treatments are helping patients regaining hair.